Growing Tomatoes in Greenhouses and Tunnels

Greenhouses and less sophisticated tunnels provide excellent growing conditions for tomatoes, even when temperatures are not closely controlled. They provide protection from wind, rain, hail and of course from the sun and from excessively cold conditions.

When tomatoes are protected from the elements, they can withstand lower temperatures than they normally would when grown out in the open – even though they do need to be heated if there is going to be protection for the plants and fruit from frost.

Many commercial tomato farmers grow their crops in greenhouses which have a scientifically controlled micro-climate. But even a sheltered environment like a plastic-covered tunnel frame gives some natural “control” of both light and moisture.

Choose a Protected Environment for your Tomatoes

Original greenhouse designs originating during the Victorian era were expensive structures that were made with steel and glass. Over time a growing number of companies have manufactured less expensive structures, some of which are available in kit form. Many of these utilise polycarbonate materials instead of glass. Some are made with aluminium (or aluminum – depending where you live!) and either glass or polycarbonate sheeting.

Greenhouses are permanent structures and can be very attractive features in the garden. The glass (or polycarbonate) transmits light during the day and can be capable of trapping quite a lot of heat at night. They are usually the same kind of height as a regular shed and so are tall enough to grow high-growing tomato plants. Large plants can grow up to 3 m or 10 ft!

Windows are often incorporated in traditional greenhouse structures, aiding ventilation. However you will still need to water the plants, and may want to install an automatic irrigation system.

In some countries, greenhouses are more commonly used when weather conditions are less than perfect, or to raise seedlings that are going to be planted out.

Walk-in tunnels are a much more modern invention, but strangely not necessarily cheaper than a small greenhouse. The thing is that tunnels are usually quite large, having been developed for commercial use. But if you have the space for one, it could be a simple alternative to a greenhouse, and could enable you to grow some superb juicy tomatoes at home!

Generally tunnels are made by stretching transparent polythene over a series of metal hoops that form the structure of the tunnel. There isn’t therefore the opportunity to make openings, except at the two ends. While tunnels are not quite as sophisticated as traditional greenhouses, they do a really good job. Another “advantage” some give is that, because they are not “permanent” you can move them if the soil becomes “diseased”. This is largely a fallacy since tunnels are BIG, and if you move them you will damage the plastic, which will then need to be replaced. At the end of the day a tunnel and a commercial greenhouse generally do the same thing.

Constructing a steel tunnel

Pests and Diseases in Greenhouses and Tunnels

Shelter in greenhouse and tunnel structures unfortunately doesn’t translate to protection from pests and diseases.

One of the stock warnings professionals give when it comes to growing tomatoes in soil beneath a growing structure is that it needs to be sterilized or regularly replaced. Greenhouses, however, are more frequently built with a solid concrete floor and then the plants are propagated in growing bags. Tunnels are usually constructed on bare earth.

Regular watering within a greenhouse or tunnel not only keeps the temperature regular and creates a nice humid environment, it also helps to curtail invasion by certain pests including the red spider mite.

Funnily enough the damaging little whitefly is more of a pest in greenhouses that it is when tomatoes are grown out in the open.

So why not do a bit more homework before you decide which way to grow tomatoes at home? It may not be worth spending money on structures; rather spend time and effort ensuring the soil in your veggie garden is good.

If you are looking for detailed, easy to understand instructions on all aspects of growing tomatoes, don’t miss our great book, How To Grow Juicy Tasty Tomatoes.

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